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. Author manuscript; available in PMC: 2022 Dec 30.
Published in final edited form as: Immunol Rev. 2022 Jul 31;311(1):39–49. doi: 10.1111/imr.13121

Figure 1. The cellular components of the neurovascular unit.

Figure 1.

The NVU is composed of a complex network of cells that are functionally diverse. ECs form the walls of blood vessels and capillaries and contribute to the formation and maintenance of the basal lamina and extracellular matrix. In addition, tight junctions formed between ECs and expression of adhesion molecules regulate BBB permeability. Pericytes reside in the capillary bed and, with regard to BBB integrity, are primarily responsible for modulation of vascular flow as well as structural changes in tight junctions and the extracellular matrix. Astrocyte endfeet cover 90–95% of the area surrounding the BBB and contribute to a variety of processes that include, but are not limited to, osmotic homeostasis, trophic factor concentration, molecular transport into and out of the perivascular space, and formation of gap junctions under neuroinflammatory conditions. Microglia have been found to cover the remaining space around BBB ECs, respond to injury and infection, and regulate tight junction formation between ECs. Neurons predominantly communicate with astrocyte endfeet and aid in regulation of tight junctions and molecular transport.